普通巫师等级考试（摘自哈利波特与凤凰社）

Meanwhile, a flourishing black-market trade in aids to concentration, mental agility and wakefulness had sprung up among the fifth- and seventh-years.Harry and Ron were much tempted by the bottle of Baruffio’s Brain Elixir offered to them by Ravenclaw sixth-year Eddie Carmichael, who swore it was solely responsible for the nine ‘Outstanding’ O.W.L.s he had gained the previous summer and was offering a whole pint for a mere twelve Galleons.Ron assured Harry he would reimburse him for his half the moment he left Hogwarts and got a job, but before they could close the deal, Hermione had confiscated the bottle from Carmichael and poured the contents down a toilet.

这段时间，五年级和七年级同学中间的黑市交易十分兴隆，交易的都是些可以让人集中精力、提神醒脑、保持清醒的东西。哈利和罗恩看到拉文克劳六年级同学埃迪·卡米切尔拿给他们的那瓶巴费醒脑剂，非常动心。埃迪一口咬定他去年夏天O.W.L.考试拿了九个“优秀”全靠这玩意儿，并提出一品脱只卖十二个金加隆。罗恩向哈利保证，他毕业一找到工作就还清他的那一半，可是没等他们成交，赫敏就把瓶子从卡米切尔手里没收了，把里面的东西全都倒进了抽水马桶。